Silicone rubber compositions are traditionally used for the sealing and encapsulation of electric and electronic parts for the purpose of preventing or retarding corrosion and degradation thereof. When electric and electronic parts are exposed to sulfur-containing gases such as sulfur gas and sulfur dioxide gas, conventional silicone rubbers fail to prevent or retard the sulfur-containing gas from reaching the electric and electronic parts. In particular, they are not effective for preventing or retarding corrosion of metal parts.